Troponin-T is an early and specific marker of myocardial infarction. Research has shown that the Troponin-T concentrations significantly increase within the first hour of an impending attack. Since the time to intervene is most critical, an implantable sensor that can detect the onset of infarction by increased Troponin-T level, could result in salvage of the myocardium. Preliminary results in our laboratory have shown the feasibility of a optical resonance energy transfer (RET) sensor to detect Troponin-T, but the biocompatibility and response of the sensor in blood need to be addressed. The goal of this research is to fabricate and characterize a Troponin-T biosensor while engineering surface modifications to enhance biocompatibility. The central hypothesis is that enhanced sensor performance and improved biocompatibility can be achieved by integrating Troponin-T biological sensing elements directly into the surface modification so that coatings can be avoided. The specific aims of this project are to: (1) design and develop a surface modified biosensor that can detect Troponin-T levels in blood, (2) achieve optimal energy transfer for strong signal response by optimizing and characterizing the grafting density and functionality of the immobilized peptides and biological sensing elements, and (3) perform in vivo studies to assess blood-material compatibility and sensor response. The information gained will advance the scientific knowledge of implantable biosensor design and drive the field to further investigate surface modifications for a variety of implantable sensors.